Environmental control system tri-heat exchanger

ABSTRACT

A heat exchanger assembly for an aircraft includes a first heat exchanger with a first hot air circuit, a second heat exchanger with a second hot air circuit, a third heat exchanger with a third hot air circuit, and a cold circuit. The first heat exchanger is in fluid communication with a source of bleed air from the engine. The second heat exchanger is disposed adjacent to and in fluid communication with the first heat exchanger. The third heat exchanger is disposed adjacent to and in fluid communication with the second heat exchanger. The first, second, and third heat exchangers are fluidly connected in series. The cold air circuit passes through each of the first, second, and third heat exchangers. The first, second, and third heat exchangers are in cross-flow communication with the cold air circuit.

BACKGROUND

The present disclosure relates to heat exchangers. More particularly,the present disclosure relates to a heat exchanger assembly for anenvironmental control system (“ECS”) of an aircraft.

The ECS, including the ram air fan assembly, aboard an aircraft providesconditioned air to an aircraft cabin. Conditioned air is air at adesired temperature, pressure, and humidity for aircraft passengercomfort. Compressing ambient air at flight altitude heats the resultingpressurized air sufficiently that it must be cooled, even if the ambientair temperature is very low. Thus, under most conditions, heat must beremoved from air by the ECS before the air is delivered to the aircraftcabin. As heat is removed from the air, it is dissipated by the ECS intoa separate stream of air that flows into the ECS, across heat exchangersin the ECS, and out of the aircraft, carrying the excess heat with it.Under conditions where the aircraft is moving fast enough, the pressureof air ramming into the aircraft is sufficient to move enough airthrough the ECS and over the heat exchangers to remove the excess heat.

In existing heat exchanger assemblies with more than one heat exchanger,the individual heat exchanger circuits are sometimes separable andbolted together. Intermediate flanges and seals between adjacent heatexchangers are bulky, heavy, and provide increased chance of leakage orfailure of the intermediate flanges and seals. Additionally,discontinuous heat transfer fins across the assembly can causeparticulates to become trapped between adjacent heat exchangers.

SUMMARY

A heat exchanger assembly for an ECS includes a first heat exchangerwith a first hot air circuit, a second heat exchanger with a second hotair circuit, a third heat exchanger with a third hot air circuit, and acold circuit. The first heat exchanger is in fluid communication with asource of bleed air from the engine. The second heat exchanger isdisposed adjacent to and in fluid communication with the first heatexchanger. The third heat exchanger is disposed adjacent to and in fluidcommunication with the second heat exchanger. The first, second, andthird heat exchangers are fluidly connected in series. The cold aircircuit passes through each of the first, second, and third heatexchangers. The first, second, and third heat exchangers are incross-flow communication with the cold air circuit.

A method of transferring thermal energy in an environmental controlsystem includes passing hot air of a first hot air circuit through hotlayers of a first heat exchanger of the environmental control system.Hot air of a second hot air circuit is passed through hot layers of asecond heat exchanger of the environmental control system. Hot air of athird hot air circuit is passed through hot layers of a third heatexchanger of the environmental control system. The first, second, andthird heat exchangers are fluidly connected in series and are brazedtogether to form a single unitized tri-heat exchanger. Cold air of acold air circuit is passed through cold layers of each of the first,second, and third heat exchangers. A direction of flow of the cold aircircuit is perpendicular to directions of flow of the first, second, andthird hot air circuits.

A heat exchanger assembly for an aircraft includes a bleed air heatexchanger, a fresh air heat exchanger, a chiller heat exchanger, and acold air circuit. The bleed air heat exchanger is in fluid communicationwith a source of bleed air from the aircraft and is configured to directa first flow of air. The fresh air heat exchanger is disposed adjacentto and in fluid communication with the bleed air heat exchanger. Thefresh air heat exchanger is configured to direct a second flow of air.The chiller heat exchanger is disposed adjacent to and in fluidcommunication with the fresh air heat exchanger. The chiller heatexchanger is configured to direct a third flow of air. The bleed air,fresh air, and chiller heat exchangers are brazed together to form asingle unitized tri-heat exchanger. The cold air circuit passes througheach of the bleed air, fresh air, and chiller heat exchangers. Adirection of flow of the cold air circuit is perpendicular to thedirections of the first, second, and third flows of air such that thebleed air, fresh air, and chiller heat exchangers are in cross-flowcommunication with the cold air circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an ECS pack with a heat exchangerassembly.

FIG. 1B is another perspective view of the ECS pack with an inletplenum.

FIG. 2 is an enlarged perspective view of a portion of the heatexchanger assembly with a plenum.

FIG. 3A is a cross-section view of a cold layer of the heat exchangerassembly taken along section line 3A-3A shown in FIG. 2.

FIG. 3B is a cross-section view of a hot layer of the heat exchangerassembly taken along section line 3B-3B shown in FIG. 2.

FIG. 4 is cross-section perspective view of a portion of the heatexchanger assembly taken along section line Z-Z shown in FIG. 2.

FIG. 5 is cross-section perspective view of a portion of the heatexchanger assembly taken along section line Y-Y shown in FIG. 2.

FIG. 6A is a cross-sectional view of the plenum attached to an end sheetof the ECS pack.

FIG. 6B is a cross-sectional view of the plenum attached to the endsheet of the ECS pack with a core band.

FIG. 7A is a plan view of the inlet plenum and the heat exchangerassembly.

FIG. 7B is an end view of the inlet plenum and the heat exchangerassembly.

FIG. 8A is a perspective view of the inlet plenum of the ECS pack.

FIG. 8B is another perspective view of the inlet plenum of the ECS pack.

DETAILED DESCRIPTION

FIG. 1A is a perspective view of ECS pack 10 with heat exchangerassembly 12 and shows ECS pack 10, heat exchanger assembly 12 (withchiller heat exchanger 14, fresh air heat exchanger 16, and bleed airheat exchanger 18), external plenum 20, FIDH 22 (fan inlet diffuserhousing), ACM 24 (air cycle machine), and power turbine 26. FIG. 1B isanother perspective view of ECS pack 10 and shows ECS pack 10, heatexchanger assembly 12 (with chiller heat exchanger 14, fresh air heatexchanger 16, and bleed air heat exchanger 18), fan inlet diffuserhousing 22, ACM 24 (air cycle machine), power turbine 26, and inletplenum 28. FIGS. 1A and 1B show the same or similar elements and will bediscussed in unison.

ECS pack 10 is an environmental control system. In this non-limitingembodiment, ECS pack 10 is an environmental control system for anaircraft. Heat exchanger assembly 12 is an assembly of three heatexchanger units. Chiller heat exchanger 14, fresh air heat exchanger 16,and bleed air heat exchanger 18 are heat exchangers each with aplurality of fins for transferring thermal energy between the fins and afluid. External plenum 20 is a semi-circular pressure vessel. FIDH 22 isa fan inlet diffuser housing. ACM 24 is an air cycle machine. Powerturbine 26 is a rotary device including a component configured to createpower by rotating in response to a fluid flowing through power turbine26. Inlet plenum 28 is an inlet housing or conduit. As will be discussedwith respect to FIGS. 7A through 8B, inlet plenum 28 includes two inletsand one outlet.

ECS pack 10 is mounted within a portion of an aircraft. ECS pack 10 isfluidly connected to numerous fluid sources such as an engine, anauxiliary power unit, a source of ambient air, a cabin, a cockpit,and/or a source of ram air of the aircraft. Heat exchanger assembly 12is mounted within a portion of ECS pack 10. Chiller heat exchanger 14 isdisposed adjacent to and in contact with fresh air heat exchanger 16.Chiller heat exchanger 14 is fluidly connected to a bleed turbine (notshown) of ECS pack 10 and to bleed air heat exchanger 18 via externalplenum 20. Chiller heat exchanger 14 is also fluidly connected to inletplenum 28 via a cold circuit of heat exchanger assembly 12 that passesthrough each of chiller heat exchanger 14, fresh air heat exchanger 16,and bleed air heat exchanger 18 (as will be discussed with respect toFIG. 3A).

Fresh air heat exchanger 16 is disposed adjacent to and in contact withchiller heat exchanger 14 and bleed air heat exchanger 18. Fresh airheat exchanger 16 is fluidly connected to a fresh air compressor (notshown) and to a condenser re-heater (not shown) of ECS pack 10. Bleedair heat exchanger 18 is disposed adjacent to and in contact with freshair heat exchanger 16 and FIDH 22. Bleed air heat exchanger 18 isfluidly connected to a bleed outflow heat exchanger (not shown) and tochiller heat exchanger 14 of ECS pack 10. External plenum 20 is mountedto end portions of chiller heat exchanger 14, fresh air heat exchanger16, and bleed air heat exchanger 18.

FIDH 22 is mounted to a side of bleed air heat exchanger 18 and to aturbo fan (not shown) of ECS pack 10. FIDH 22 is fluidly connected tothe cold ram air circuit that passes through heat exchanger assembly 12.In other non-limiting embodiments, FIDH 22 can be replaced with anothercomponent or removed all together from ECS pack 10. ACM 24 is physicallyand fluidly connected to power turbine 26. Power turbine 26 is mountedto a portion of ACM 24 and is fluidly connected to ACM 24 and to inletplenum 28. Inlet plenum 28 is mounted to chiller heat exchanger 14 via apicture frame flange interface with a flange the shape of a pictureframe extending from both plenum 28 and chiller heat exchanger 14. Inletplenum 28 is fluidly connected to chiller heat exchanger 14, to a sourceof ram air, and to power turbine 26.

ECS pack 10 controls and manages the transfer of thermal energy andpressures among the different sources of air throughout the aircraft.Heat exchanger assembly 12 (with chiller heat exchanger 14, fresh airheat exchanger 16, and bleed air heat exchanger 18) functions to coolthe air flowing through each of chiller heat exchanger 14, fresh airheat exchanger 16, and bleed air heat exchanger 18. As will be discussedwith respect to FIGS. 3A and 3B, heat exchanger assembly 12 includesthree independent hot circuits that are in series cross flowcommunication with a single (cold) ram circuit.

External plenum 20 functions to transfer air from bleed air heatexchanger 18 to chiller heat exchanger 14. FIDH 22 functions to receiveand transfer air away from the cold ram air circuit of heat exchangerassembly 12. ACM 24 functions as an air conditioning pack to change tothe pressure, temperature, and/or humidity of air passing through ACM24. Inlet plenum 28 receives cooling air from two separate sources andtransfers that air into heat exchanger assembly 12. The two sources areambient ram air and exhaust air from power turbine 26.

ECS pack 10 with heat exchanger assembly 12 provides a benefit ofminimizing the overall installed volume of ECS pack 10 by eliminatingpicture frame flanges between hot passes that are often incorporated inexisting heat exchanger assemblies. For example, in one embodiment, heatexchanger assembly 12 provides approximately a 4 inch reduction in awidth of heat exchanger assembly 12 as compared to a heat exchangerassembly configuration including three separate heat exchangers boltedtogether in series. ECS pack 10 with heat exchanger assembly 12 reducesthe amount of parts by combining three cross flow heat exchangers into asingle assembly. Heat exchanger assembly 12 eliminates the need forintermediate ram flanges and seals, provides a lighter weight assembly,and reduces the amount of time necessary to assemble ECS pack 10. Theconfiguration of heat exchanger assembly 12 also improves reliability ofECS pack 10 by reducing a number of seals and potential leak sourcesbetween each of chiller heat exchanger 14, fresh air heat exchanger 16,and bleed air heat exchanger 18.

FIG. 2 is an enlarged perspective view of a portion of ECS pack 10 andshows heat exchanger assembly 12, chiller heat exchanger 14 (withchiller endwall 30, chiller inlet header 32, chiller outlet header 34,and chiller endcap 36), fresh air heat exchanger 16 (with fresh airendwall 38, fresh air inlet header 40, and fresh air outlet header 42),bleed air heat exchanger 18 (with bleed air endwall 44, bleed air inletheader 46, bleed air outlet header 48, and bleed air endcap 50),external plenum 20, FIDH 22, inlet plenum 28, end sheet 52, anddirection G of gravity.

Chiller endwall 30, fresh air endwall 38, and bleed air endwall 44 arewalls or barriers of solid material. Chiller inlet header 32, chilleroutlet header 34, fresh air inlet header 40, fresh air outlet header 42,bleed air inlet header 46, and bleed air outlet header 48 areapproximately semi-circular pieces of solid material extending along alength. In one non-limiting embodiment, chiller endcap 36 and/or bleedair endcap 50 can be cast or hydro-formed pieces of solid material thatinclude a bent, semi-circular shape. End sheet 52 is a wall or barrierof heat exchanger assembly 12. Direction G is a direction of gravityrelative to ECS pack 10 (and heat exchanger assembly 12), illustrated inthe example of FIG. 2 when the aircraft is level (e.g., on ground or instraight and level flight).

External plenum 20 is mounted to end sheet 52. In one non-limitingembodiment, external plenum 20 is welded to end sheet 52 with a filletweld. External plenum 20 is connected to end sheet 52 so as to form asealed conduit. Chiller endwall 30 is disposed on an end of chiller heatexchanger 14. Chiller inlet header 32 is disposed on a top side ofchiller heat exchanger 14. Chiller inlet header 32 is fluidly connectedto chiller heat exchanger 14 and to external plenum 20 via chillerendcap 36. Chiller outlet header 34 is disposed on a bottom side ofchiller heat exchanger 14. Chiller outlet header 34 is fluidly connectedto chiller heat exchanger 14. Chiller endcap 36 is attached to a portionof chiller inlet header 32. Chiller endcap 36 is fluidly connected tochiller inlet header 32 and to external plenum 20.

Fresh air endwall 38 is disposed on an end of fresh air heat exchanger16. Fresh air inlet header 40 is disposed on a top side of fresh airheat exchanger 16. Fresh air outlet header 42 is disposed on a bottomside of fresh air heat exchanger 16. Bleed air endwall 44 is disposed onan end of bleed air heat exchanger 18. Bleed air inlet header 46 isdisposed on a top side of bleed air heat exchanger 18. Bleed air outletheader 48 is disposed on a bottom side of bleed air heat exchanger 18.Bleed air outlet header 48 is fluidly connected to bleed air heatexchanger 18 and to external plenum 20 via bleed air endcap 50. Bleedair endcap 50 is attached to a portion of bleed air outlet header 48.Bleed air endcap 50 is fluidly connected to bleed air heat exchanger 18and to external plenum 20.

End sheet 52 is disposed on an end of heat exchanger assembly 12. Endsheet 52 is formed by chiller endwall 30, fresh air endwall 38, andbleed air endwall 44. Direction G of gravity points in a downwarddirection in FIG. 2 (e.g., when the aircraft is level, such as in levelflight or on-ground). Heat exchanger assembly 12, chiller heat exchanger14, fresh air heat exchanger 16, and bleed air heat exchanger 18 areoriented relative to gravity as shown in FIG. 2.

The sealed conduit formed by external plenum 20 and end sheet 52 isconfigured to transport a fluid (such as air) from bleed air outletheader 48 of bleed air heat exchanger 18 to chiller inlet header 32 ofchiller heat exchanger 14. Chiller endwall 30 confines and fluidly sealsa portion of chiller heat exchanger 14. Chiller inlet header 32 isconfigured to receive air from bleed air outlet header 48 and transferthe air into chiller heat exchanger 14. Chiller outlet header 34receives a flow of hot air passing through chiller heat exchanger 14.Chiller endcap 36 fluidly connects external plenum 20 to chiller inletheader 32.

Fresh air endwall 38 confines and fluidly seals a portion of fresh airheat exchanger 16. Fresh air inlet header 40 is configured to receiveair from the fresh air compressor (not shown) and transfer the air intofresh air heat exchanger 16. Fresh air outlet header 42 is configured toreceive air from fresh air heat exchanger 16 and transfer the air to thecondenser re-heater (not shown) of ECS pack 10. Bleed air endwall 44confines and fluidly seals a portion of bleed air heat exchanger 18.Bleed air inlet header 46 is configured to receive air from bleedoutflow heat exchanger (not shown) and transfer the air into bleed airheat exchanger 18. Bleed air outlet header 48 is configured to receiveair from bleed air heat exchanger 18 and transfer the air to chillerheat exchanger 14 vie external plenum 20. Bleed air endcap 50 fluidlyconnects external plenum 20 to a portion of bleed air outlet header 48.

End sheet 52 confines and fluidly seals a portion of heat exchangerassembly 12. End sheet 52 also transfers thermal energy between the airpassing through external plenum 20 and end sheet 52. The orientation ofECS pack 10 and heat exchanger assembly 12 with respect to direction Gof gravity functions to allow drainage of condensation and water in eachof chiller heat exchanger 14, fresh air heat exchanger 16, and bleed airheat exchanger 18 in a downward direction and into chiller outlet header34, fresh air outlet header 42, and bleed air outlet header 48,respectively. Though the example of FIG. 2 illustrates the direction Gof gravity in a downward direction directly toward chiller outlet header34, fresh air outlet header 42, and bleed air outlet header 48, itshould be understood that the direction G of gravity will changerelative to ECS pack 10 and heat exchanger assembly 12 as the aircraftattitude (i.e., roll, pitch, and/or yaw of the aircraft) changes. Thatis, as the roll, pitch, and/or yaw of the aircraft changes, thedirection G of gravity will change relative to ECS pack 10 and heatexchanger assembly 12, but will continue to have a component in thedownward direction (i.e., toward chiller outlet header 34, fresh airoutlet header 42, and bleed air outlet header 48). Accordingly, even asthe aircraft attitude changes during flight, the direction G of gravityhas a component in the direction of flow of the hot air toward chilleroutlet header 34, fresh air outlet header 42, and bleed air outletheader 48.

In existing heat exchanger assemblies with directions of flow not in thesame direction as gravity, water tends to accumulate onto the fins ofthe heat exchangers. This build-up of water on the fins of the heatexchangers can cause functionality issues as well as outright failure ofthe heat exchangers or connected ACM of the system. ECS pack 10 withheat exchanger assembly 12 oriented to have directions of hot airflow ina same direction as gravity allows for any water attached to the fins ofchiller heat exchanger 14, fresh air heat exchanger 16, and bleed airheat exchanger 18 to more easily flow into chiller outlet header 34,fresh air outlet header 42, and bleed air outlet header 48,respectively. Once the accumulated water is collected into the chilleroutlet header 34, fresh air outlet header 42, and/or bleed air outletheader 48, the water can be easily drained and removed from heatexchanger assembly 12, thereby eliminating the potential negativeeffects the accumulated water could have if not removed from heatexchanger assembly 12.

FIG. 3A is a cross-section view of cold layer 54 of heat exchangerassembly 12 taken along section line 3A-3A shown in FIG. 2. FIG. 3Ashows heat exchanger assembly 12 (with width W₁₂), chiller heatexchanger 14 (with chiller inlet header 32 and chiller outlet header34), fresh air heat exchanger 16 (with fresh air inlet header 40 andfresh air outlet header 42), bleed air heat exchanger 18 (with bleed airinlet header 46 and bleed air outlet header 48), direction G of gravity,cold fins 56, cold air circuit 58, top closure bar 60, bottom closurebar 62, ram air inlet 64, ram air outlet header 66, first top core band68, second top core band, 70, first bottom core band, 72, second bottomcore band 74, first top Y-septum 76, second top Y-septum 78, firstbottom Y-septum 80, and second bottom Y-septum 82.

Width W₁₂ is a width of heat exchanger assembly 12. Cold layer 54 is asingle cross-section layer of heat exchanger assembly 12 that includescold fins 56 for transfer of thermal energy. Cold fins 56 are wavysheets of solid material such as metal configured to transfer thermalenergy between cold fins 56 and a fluid passing across cold fins 56.Cold air circuit 58 includes a continuous fin allowing ram air to flowthrough heat exchanger assembly 12, picking up heat rejected by threehot circuits passing through chiller heat exchanger 14, fresh air heatexchanger 16, and bleed air heat exchanger 18. Top closure bar 60 andbottom closure bar 62 are flat, elongated pieces of solid material. Ramair inlet 64 is a fluidic inlet. Ram air outlet header 66 is a fluidicoutlet.

First top core band 68, second top core band 70, first bottom core band72, and second bottom core band 74 are elongated pieces of solidmaterial that include a 90 degree bend cross-section. First top Y-septum76, second top Y-septum 78, first bottom Y-septum 80, and second bottomY-septum 82 are elongated pieces of solid material that include aY-shaped cross-section. In one non-limiting embodiment, any of first topY-septum 76, second top Y-septum 78, first bottom Y-septum 80, andsecond bottom Y-septum 82 can be formed by an extrusion process.

Width W₁₂ spans across widths of chiller heat exchanger 14, fresh airheat exchanger 16, and bleed air heat exchanger 18. Chiller inlet header32 is mounted to first top core band 68 and to first top Y-septum 76with welds. In one non-limiting embodiment, chiller inlet header 32 canbe mounted to either first top core band 68 or to first top Y-septum 76with either a butt weld or a groove weld. Chiller outlet header 34 ismounted to first bottom core band 72 and to first bottom Y-septum 80with welds. In one non-limiting embodiment, chiller outlet header 34 canbe mounted to either first bottom core band 72 or to first bottomY-septum 80 with either a butt weld or a groove weld.

Fresh air inlet header 40 is mounted to first top Y-septum 76 and tosecond top Y-septum 78 with welds. In one non-limiting embodiment, freshair inlet header 40 can be mounted to either first top Y-septum 76 or tosecond top Y-septum 78 with either a butt weld or a groove weld. Freshair outlet header 42 is mounted to first bottom Y-septum 80 and tosecond bottom Y-septum 82 with welds. In one non-limiting embodiment,fresh air outlet header 42 can be mounted to either first bottomY-septum 80 or to second bottom Y-septum 82 with either a butt weld or agroove weld.

Bleed air inlet header 46 is mounted to second top Y-septum 78 and tosecond top core band 70 with welds. In one non-limiting embodiment,bleed air inlet header 46 can be mounted to either second top Y-septum78 or to second top core band 70 with either a butt weld or a grooveweld. Bleed air outlet header 48 is mounted to second bottom Y-septum 82and to second bottom core band 74 with welds. In one non-limitingembodiment, bleed air outlet header 48 can be mounted to either secondbottom Y-septum 82 or to second bottom core band 74 with either a buttweld or a groove weld.

Cold layer 54 is one of a plurality of cold layers 54 mounted withinheat exchanger assembly 12 in an alternating pattern with a plurality ofhot layers. Cold layer 54 is fluidly connected to inlet plenum 28 (notshown in FIG. 3A) via ram air inlet 64 and to FIDH 22 (not shown in FIG.3A) via ram air outlet header 66. Cold fins 56 are mounted as a part ofcold layer 54. Cold fins 56 are in fluid communication with cold aircircuit 58. Cold air circuit 58 passes into cold layer 54 through ramair inlet 64, across cold fins 56, and out of cold layer 54 through ramair outlet header 66.

Top closure bar 60 is mounted to cold layer 54 along a top side of coldlayer 54 (top as shown in FIG. 3A). Top closure bar 60 is in fluidcommunication with cold circuit 58. Top closure bar 60 is attached andconnected to first top core band 68, second top core band 70, first topY-septum 76, and second top Y-septum 78. Bottom closure bar 62 ismounted to cold layer 54 along a bottom side of cold layer 54 (bottom asshown in FIG. 3A). Bottom closure bar 62 is in fluid communication withcold circuit 58. Bottom closure bar 62 is attached and connected tofirst bottom core band 72, second bottom core band 74, first bottomY-septum 80, and second bottom Y-septum 82.

Ram air inlet 64 is disposed on an upstream, or left side (left as shownin FIG. 3A), of cold layer 54. Ram air inlet 64 is fluidly connected toinlet plenum 28 (not shown in FIG. 3A) and to cold fins 56. Ram airoutlet header 66 is disposed on a downstream, or right side (right asshown in FIG. 3A), of cold layer 54. Ram air outlet header 66 is fluidlyconnected to FIDH 22 (not shown in FIG. 3A) and to cold fins 56.

First top core band 68 is mounted to a top left-hand corner of coldlayer 54. First top core band 68 is attached and connected to topclosure bar 60 and to a portion of chiller inlet header 32. Second topcore band 70 is mounted to a top right-hand corner of cold layer 54.Second top core band 70 is attached and connected to top closure bar 60and to a portion of bleed air inlet header 46. First bottom core band 72is mounted to a bottom left-hand corner of cold layer 54. First bottomcore band 72 is attached and connected to bottom closure bar 62 and to aportion of chiller outlet header 34. Second bottom core band 74 ismounted to a bottom right-hand corner of cold layer 54. Second bottomcore band 74 is attached and connected to bottom closure bar 62 and to aportion of bleed air outlet header 48.

First top Y-septum 76 is attached and connected to chiller inlet header32, fresh air inlet header 40, and to top closure bar 60. In this nonlimiting embodiment, first top Y-septum 76 is welded to top closure bar60 with either a groove weld or two fillet welds. Second top Y-septum 78is attached and connected to fresh air inlet header 40, bleed air inletheader 46, and to top closure bar 60. In this non limiting embodiment,second top Y-septum 78 is welded to top closure bar 60 with either agroove weld or two fillet welds. First bottom Y-septum 80 is attachedand connected to chiller outlet header 34, fresh air outlet header 42,and to bottom closure bar 62. In this non limiting embodiment, firstbottom Y-septum 80 is welded to bottom closure bar 62 with either agroove weld or two fillet welds. Second bottom Y-septum 82 is attachedand connected to fresh air outlet header 42, bleed air outlet header 48,and to bottom closure bar 62. In this non limiting embodiment, secondbottom Y-septum 82 is welded to bottom closure bar 62 with either agroove weld or two fillet welds.

Cold layer 54 receives cold air circuit 58 from inlet plenum 28 andguides cold air circuit across cold fins 56 so as to transfer thermalenergy from cold fins 56 into the air of cold air circuit 58. Cold fins56 transfer thermal energy to the air of cold air circuit 58. Cold aircircuit 58 is drawn through cold layer 54 so as to receive thermalenergy from cold fins 56 so as to result in a reduction in the amount ofthermal energy in cold fins 56. Top closure bar 60 and bottom closurebar 62 provide fluidic barriers for containing cold circuit 58 betweentop closure bar 60 and bottom closure bar 62 as cold air circuit 58passes through cold layer 54.

Ram air inlet 64 provides a fluidic inlet through which cold air circuit58 enters into cold layer 54 and into contact with cold fins 56. Ram airoutlet header 66 provides a fluidic outlet through which cold aircircuit 58 exits out of cold layer 54. First top core band 68, secondtop core band 70, first bottom core band 72, and second bottom core band74 provide structural support for the components of cold layer 54. Firsttop Y-septum 76, second top Y-septum 78, first bottom Y-septum 80, andsecond bottom Y-septum 82 provide mount points for components of coldlayer 54 and of heat exchanger assembly 12. First top Y-septum 76,second top Y-septum 78, first bottom Y-septum 80, and second bottomY-septum 82 also provide a continued curved surface that is similar tothe curved inner surfaces of the inlet and outlet headers of heatexchanger assembly 12.

Cold layer 54 of heat exchanger assembly 12 provides a single continuousram fin across which cold air circuit 58 flows. In existingconfigurations, a discontinuous ram fin leads to particulates becomingtrapped in the points of discontinuity. With a single continuous ramfin, cold layer 54 is less susceptible to clogging and failure due toparticulate blockage. Additionally, the welded interfaces among thecomponents of cold layer of heat exchanger assembly 12 reduced thenumber of parts as well as width W₁₂ and corresponding pack volume ofECS pack 10.

FIG. 3B is a cross-section view of hot layer 84 of heat exchangerassembly 12 taken along section line 3B-3B shown in FIG. 2. FIG. 3Bshows heat exchanger assembly 12 (with width W₁₂), chiller heatexchanger 14 (with chiller inlet header 32 and chiller outlet header34), fresh air heat exchanger 16 (with fresh air inlet header 40 andfresh air outlet header 42), bleed air heat exchanger 18 (with bleed airinlet header 46 and bleed air outlet header 48), direction G of gravity,ram air inlet 64, ram air outlet header 66, first top core band 68,second top core band, 70, first bottom core band, 72, second bottom coreband 74, first top Y-septum 76, second top Y-septum 78, first bottomY-septum 80, second bottom Y-septum 82, hot layer 84, hot fins 86,chiller air circuit 88, fresh air circuit 90, bleed air circuit 92,reinforcing bars 94, redistribution slots 96, first closure bar 98,second closure bar 100, third closure bar 102, and fourth closure bar104.

Hot layer 84 is a single cross-section layer of heat exchanger assembly12 that includes hot fins 86 for transfer of thermal energy. Hot fins 86are wavy sheets of solid material such as metal configured to transferthermal energy between hot fins 86 and a fluid passing across hot fins86. Chiller air circuit 88, fresh air circuit 90, and bleed air circuit92 are fluidic pathways. Reinforcing bars 94 are bars of solid material.Redistribution slots 96 are rectangular slits or openings. First closurebar 98, second closure bar 100, third closure bar 102, and fourthclosure bar 104 are flat, elongated pieces of solid material.

Hot layer 84 is mounted within heat exchanger assembly 12 in analternating pattern with a plurality of cold layers 54. Hot fins 86 aremounted as a part of hot layer 84 and are in fluid communication withchiller air circuit 88, fresh air circuit 90, and bleed air circuit 92.Hot fins 86 are located in each of chiller heat exchanger 14, fresh airheat exchanger 16, and bleed air heat exchanger 18. Hot fins 86 ofchiller heat exchanger 14, fresh air heat exchanger 16, and bleed airheat exchanger 18 are brazed together to form a unitized assembly suchthat chiller heat exchanger 14, fresh air heat exchanger 16, and bleedair heat exchanger 18 are a single unit without flanges or attachmenthardware therebetween.

Chiller air circuit 88 passes into hot layer 84 through chiller inletheader 32, across hot fins 86 of chiller heat exchanger 14, and out ofhot layer 84 through chiller outlet header 34. Fresh air circuit 90passes into hot layer 84 through fresh air inlet header 40, across hotfins 86 of fresh air heat exchanger 16, and out of hot layer 84 throughfresh air outlet header 42. Bleed air circuit 92 passes into hot layer84 through bleed air inlet header 46, across hot fins 86 of bleed airheat exchanger 18, and out of hot layer 84 through bleed air outletheader 46.

Reinforcing bars 94 are disposed within portions of heat exchangerassembly 12 at locations where components of heat exchanger assembly 12are connected together. Reinforcing bars 94 are mounted to portions offirst closure bar 98, second closure bar 100, third closure bar 102, andfourth closure bar 104 at locations adjacent to first top core band 68,second top core band 70, first bottom core band 72, second bottom coreband 74, first top Y-septum 76, second top Y-septum 78, first bottomY-septum 80, and second bottom Y-septum 82. Redistribution slots 96 aredisposed in portions of hot fins 86 that are immediately adjacentreinforcing bars 94 along the directions of flow of chiller, fresh, andbleed air circuits 88, 90, and 92.

First top core band 68 and first bottom core band 72 are mounted tofirst closure bar 98. First closure bar 98 is located to the left ofchiller air circuit 88 (to the left as shown in FIG. 3B). First topY-septum 76 and first bottom Y-septum 80 are mounted to second closurebar 100. Second top Y-septum 78 and to second bottom Y-septum 82 aremounted to third closure bar 102. Second top core band 70 and to secondbottom core band 74 are mounted to fourth closure bar 104.

Hot layer 84 receives chiller air circuit 88 from chiller heat exchanger14, fresh air circuit 90 from fresh air heat exchanger 16, and bleed aircircuit 92 from bleed air heat exchanger 18. Hot layer 84 then guideschiller air circuit 88, fresh air circuit 90, and bleed air circuit 92across hot fins 86 so as to transfer thermal energy from hot fins 86into the air of chiller air circuit 88, fresh air circuit 90, and bleedair circuit 92. Hot fins 86 transfer thermal energy to the air ofchiller air circuit 88, fresh air circuit 90, and bleed air circuit 92.

Chiller air circuit 88, fresh air circuit 90, and bleed air circuit 92are drawn through hot layer 84 so as to transfer thermal energy to hotfins 86 so as to result in a reduction in the amount of thermal energyin chiller air circuit 88, fresh air circuit 90, and bleed air circuit92. Also, the directions of chiller air circuit 88, fresh air circuit90, and bleed air circuit 92 are in the same downward direction as thedirection G of gravity to promote condensed water flow in a downwarddirection.

Reinforcing bars 94 reinforce and provide additional structural supportto portions of heat exchanger assembly 12 at locations where componentsof heat exchanger assembly 12 form connection points. Redistributionslots 96 redistribute or allow portions of chiller air circuit 88, freshair circuit 90, and bleed air circuit 92 to drop behind reinforcing bars94 so as to transport portions of chiller air circuit 88, fresh aircircuit 90, and bleed air circuit 92 to hot fins 86 that are positioneddownstream/upstream of reinforcing bars 94. Without redistribution slots96, hot fins 86 placed in downstream/upstream alignment with reinforcingbars 94 would not receive any of the flows from chiller air circuit 88,fresh air circuit 90, and bleed air circuit 92 because reinforcing bars94 would block flow moving in an up to down direction (up and downdirections as shown in FIG. 3B).

First closure bar 98 and second closure bar 100 provide fluidic barriersfor containing chiller air circuit 88 between first closure bar 98 andsecond closure bar 100 as chiller air circuit 88 passes through hotlayer 84. Third closure bar 102 provides a fluidic barrier forcontaining fresh air circuit 90 between second closure bar 100 and thirdclosure bar 102 as fresh air circuit 90 passes through hot layer 84.Fourth closure bar 104 provides a fluidic barrier for containing bleedair circuit 92 between third closure bar 102 and fourth closure bar 104as bleed air circuit 92 passes through hot layer 84.

The unitized configuration of heat exchanger assembly removes interfaceflanges and associated attachment hardware necessary in existing heatexchanger assemblies without three heat exchangers brazed together toform a single, unitized assembly. The removal of interface flanges andhardware reduces width W₁₂ of heat exchanger assembly and reduces theoverall weight of heat exchanger 12 and ECS pack 10. Redistributionslots 96 maximize available core channels in hot layer 84 otherwiseobstructed by reinforcing bars 94 and fin run out. Orienting thedirections of chiller air circuit 88, fresh air circuit 90, and bleedair circuit 92 to be the same direction as direction G of gravityminimizes the risk of condensed water retention within heat exchangerassembly 12.

FIG. 4 is cross-section perspective view of a portion of heat exchangerassembly 12 taken along section line Z-Z shown in FIG. 2 and shows heatexchanger assembly 12, chiller heat exchanger 14 (with chiller endwall30, chiller inlet header 32, chiller outlet header 34, and chillerendcap 36), fresh air heat exchanger 16 (with fresh air endwall 38,fresh air inlet header 40, and fresh air outlet header 42), externalplenum 20, inlet plenum 28, end sheet 52, and direction G of gravity.

In this view, the cross-section shape of external plenum 20 is seen toinclude a semi-circle. In other non-limiting embodiments, thecross-section shape of external plenum 20 can include other geometries.In this non-limiting embodiment, external plenum 20 is attached tochiller endcap 36 and to end sheet 52 with welds. External plenum 20fluidly (and/or pneumatically) connects bleed air outlet header 48 (notshown in FIG. 4) to chiller inlet header 32. Bleed air endcap 50 (notshown in FIG. 4) transitions flow from bleed air outlet header 48 (notshown in FIG. 4) to external plenum 20. Chiller endcap 36 transitionsthe flow from external plenum 20 into Chiller inlet header 32.

Benefits of incorporating external plenum 20 into heat exchangerassembly 12 include minimizing installed system volume, leakage andweight versus and an external duct run as well as eliminating a need forexternal and/or separable ducting, couplings, flanges and seals. Inother non-limiting embodiments, bypass lines can intersect with externalplenum 20 to extract bleed outlet air to other parts of ECS pack 10. Inother non-limiting embodiments, external plenum 20 can be applied toother heat exchanger configurations such as a dual-heat exchanger,condenser/re-heater assemblies, etc. Other benefits of external plenum20 include reducing installed pack volume of ECS pack 10; reducing partscount by eliminating separate loose ducting, flanges, seals andcouplings; reducing the weight of ECS pack 10; reducing assembly time ofECS pack 10; and improving reliability of ECS pack 10 by reducing thenumber of seals and potential leakage sources of heat exchanger assembly12.

FIG. 5 is cross-section perspective view of a portion of heat exchangerassembly 12 taken along section line Y-Y shown in FIG. 2 and shows heatexchanger assembly 12, chiller heat exchanger 14 (with chiller endwall30 and chiller outlet header 34), fresh air heat exchanger 16 (withfresh air endwall 38 and fresh air outlet header 42), bleed air heatexchanger 18 (with bleed air endwall 44, bleed air outlet header 48, andbleed air endcap 50), external plenum 20, inlet plenum 28, end sheet 52,and direction G of gravity. FIG. 5 provides an additional view of theinterface between external plenum 20 and end sheet 52. External plenum20 includes a semi-circular shape with a flat sidewall such that endsheet 52 of the heat exchanger assembly forms the flat sidewall ofexternal plenum 20. In this non-limiting embodiment, external plenum 20is mounted to end sheet 52 with a fillet weld.

External plenum 20 is attached to end sheet 52 along an entire length ofexternal plenum 20. External plenum 20 and end sheet 52 form a sealedconduit configured to transport a fluid from bleed air outlet header 48of bleed air heat exchanger 18 to chiller inlet header 32 of the ofchiller heat exchanger 14. In addition to transferring air from bleedair outlet header 48 to chiller inlet header 32, external plenum 20 alsoallows air within external plenum 20 to be in contact with each ofchiller endwall 30, fresh air endwall 38, and bleed air endwall 44 whichallows thermal energy to be transferred between the air in externalplenum 20 and each of chiller endwall 30, fresh air endwall 38, andbleed air endwall 44.

A method of managing a fluid with external plenum 20 of heat exchangerassembly 12 includes inserting air into bleed air heat exchanger 18. Theair is drawn out of bleed air heat exchanger 18, through bleed airoutlet header 48, and into external plenum 20. The air is passed throughexternal plenum 20. As the air is passed through external plenum 20, theair is passed across and in contact with end sheet 52. The air is drawninto chiller inlet header 32 and is then transferred into chiller heatexchanger 14.

FIG. 6A is a cross-sectional view of external plenum 20 attached to endsheet 52. In this non-limiting embodiment, external plenum 20 is mountedto end sheet 52 with a fillet weld. FIG. 6B is a cross-sectional view ofexternal plenum 20 attached to end sheet 52 with core bands 106. In thisnon-limiting embodiment, external plenum 20 is mounted to core bands 106with a fillet weld and with core bands 106 being welded to end sheet 52with a butt weld. The types of welds used to attach external plenum toend sheet 52 of heat exchanger assembly 12 can be selected based onoperational, thermal, and weight parameters of ECS pack 10.

FIG. 7A is a plan view of inlet plenum 28 attached to heat exchangerassembly 12 and shows heat exchanger assembly 12, chiller heat exchanger14 (with chiller inlet header 32 and chiller endcap 36), fresh air heatexchanger 16 (with fresh air inlet header 40), bleed air heat exchanger18 (with bleed air inlet header 46), inlet plenum 28 (with housing 108,first inlet 110, second inlet 112, and outlet 114), ram air inlet 64,and ram air outlet header 66. In this non-limiting embodiment, FIG. 7Aincludes an embodiment of heat exchanger assembly 12 without externalplenum 20.

Housing 108 is a container with walls of solid material. In onenon-limiting embodiment, housing 108 can include a metallic, molded orcomposite construction. First inlet 110 and second inlet 112 are fluidicinlets or apertures. Outlet 114 is a fluidic outlet or aperture. Outlet114 includes a picture frame flange. Housing 108 is mounted to chillerheat exchanger 14 via a flanged interface. First inlet 110 and secondinlet 112 are disposed in a portion of inlet plenum 28. First inlet 110and second inlet 112 are fluidly connected to outlet 114 via housing108. First inlet 110 is fluidly connected to an exhaust of the powerturbine (not shown) of ECS pack 10. Second inlet is fluidly connected toa source of ram air such as a NACA (U.S. National Advisory Committee forAeronautics) scoop. Outlet 114 is fluidly connected to ram air inlet 64of heat exchanger assembly 12.

Housing 108 is configured to direct a mixed air stream of air sourcesfrom both first inlet 110 and second inlet 112 to outlet 114 and to ramair inlet 64 of heat exchanger assembly 12. First inlet 110 provides afirst source of cool air to housing 108 of inlet plenum 28. Second inlet112 provides a second source of cool air to housing 108 of inlet plenum28. Outlet 114 directs the mixed air stream from housing 108 to ram airinlet 64 of heat exchanger assembly 12.

Inlet plenum 28 of ECS pack 10 provides two independent cooling streamsthat are joined at a common plenum to be fed into heat exchangerassembly 12. Additionally, the contoured geometry of housing 108 ofinlet plenum 28 is optimized so as to aid in directing a flow of airacross a face of ram air inlet 64 of heat exchanger assembly 12.

FIG. 7B is an end view of inlet plenum 28 attached to heat exchangerassembly 12 and shows heat exchanger assembly 12, chiller heat exchanger14 (with chiller inlet header 32 and chiller endcap 36), fresh air heatexchanger 16 (with fresh air inlet header 40), bleed air heat exchanger18 (with bleed air inlet header 46), inlet plenum 28 (with first inlet110, second inlet 112, outlet 114, access panel 116, and gasket 118),ram air inlet 64, and ram air outlet header 66. In this non-limitingembodiment, FIG. 7B includes an embodiment of heat exchanger assembly 12without external plenum 20.

Access panel 116 is a detachable door. Gasket 118 is a seal. Accesspanel 116 is mounted in a portion of housing 108 of inlet plenum 28.Access panel 116 is located in an opening in housing 108. Access panel116 can be removable from housing 108, or otherwise attached so as to befully or partially removed from the opening. Gasket 118 is mounted alongan edge of access panel 116. Access panel 116 provides accessibilityinto housing 108. Gasket 118 provides a fluidic seal between housing 108and access panel 116. Access panel 116 allows a user to access theinside of housing 108 to remove foreign object debris from housing 108or from portions of ram air inlet 64 of heat exchanger assembly 12.

FIG. 8A is a perspective view of inlet plenum 28 of ECS pack 10 andshows inlet plenum 28, first inlet 110, second inlet 112, outlet 114,access panel 116, gasket 118, sidewall 120, inlet feature 122, andnozzle 124. FIG. 8B is another perspective view of inlet plenum 28 ofECS pack 10 and shows inlet plenum 28, first inlet 110, second inlet112, outlet 114, sidewall 120, and inlet feature 122. FIGS. 8A and 8Bshow the same or similar elements and will be discussed in unison.

Sidewall 120 is a tapered wall of housing 108. Inlet feature 122 is acurved or cupped portion of housing 108. A cross-sectional shape ofinlet feature 122 includes a partially circular or partially ellipticalshape. Nozzle 124 is a spout configured to spray a fluid. In thisnon-limiting embodiment, housing 108 includes a single nozzle 124. Inother non-limiting embodiment, housing 108 can include more than onenozzle 124. Sidewall 120 is mounted to a side of housing 108. Inletfeature 122 is formed in a portion of housing 108. Nozzle 124 is mountedinside of housing 108.

A contour and shape of sidewall 120 is configured to combine a firststream of air from first inlet 110 and a second stream of air fromsecond inlet 112 into a mixed air stream. The contour and shape ofsidewall 120 is also configured to direct the mixed air stream towardsoutlet 114 and into ram air inlet 64 of heat exchanger assembly 12 byturning the mixed air stream. Inlet feature 122 is configured to directthe first stream of air from first inlet 110 towards a forward end ofheat exchanger assembly 12. Nozzle 124 is configured to disperse waterfrom a water extractor of ECS pack 10 into air passing through the inletplenum.

Inlet feature 122 directs the first stream of air to a portion of outlet114 that enhances the cooling effects of the mixed air stream exitinghousing 108 and that flows into heat exchanger assembly 12. Fluidsprayed from nozzle 124 provides addition thermal energy transfer toenhance system cooling performance of heat ECS pack 10. The location ofnozzle 124 within housing 108 can be adjusted so as to optimize thecooling effects of fluid dispensed from nozzle 124.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A heat exchanger assembly for an aircraft includes a first heatexchanger with a first hot air circuit, a second heat exchanger with asecond hot air circuit, a third heat exchanger with a third hot aircircuit, and a cold circuit. The first heat exchanger is in fluidcommunication with a source of bleed air from the engine. The secondheat exchanger is disposed adjacent to and in fluid communication withthe first heat exchanger. The third heat exchanger is disposed adjacentto and in fluid communication with the second heat exchanger. The first,second, and third heat exchangers are fluidly connected in series. Thecold air circuit passes through each of the first, second, and thirdheat exchangers. The first, second, and third heat exchangers are incross-flow communication with the cold air circuit.

The heat exchanger assembly of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components.

The first heat exchanger can comprise of a bleed air heat exchanger,wherein the second heat exchanger can comprise of a fresh air heatexchanger, and/or wherein the third heat exchanger can comprise of achiller heat exchanger.

A plurality of hot layers can comprise a plurality of hot fins, whereinthe first, second, and/or third hot air circuits can be in fluidcommunication with the plurality of hot layers; and/or a plurality ofcold layers can comprise a plurality of cold fins, wherein the cold aircircuit can be in fluid communication with the plurality of cold layers.

Each cold fin of the pluralities of cold fins can be continuous and canextend across an entire width of the heat exchanger assembly.

The first, second, and/or third heat exchangers can be brazed togetherto form a single unitized tri-heat exchanger.

A first closure bar can be disposed between the first and second hot aircircuits, wherein the first closure bar prevents fluid communicationacross the first closure bar between the first and second hot aircircuits; a second closure bar can be disposed between the second andthird hot air circuits, wherein the second closure bar can prevent fluidcommunication across the second closure bar between the second and thirdhot air circuits; a first top Y-septum can be welded to a top end of thefirst closure bar; a second top Y-septum can be welded to a top end ofthe second closure bar; a first bottom Y-septum can be welded to abottom end of the first closure bar; and/or a second bottom Y-septum canbe welded to a bottom end of the second closure bar.

A first top header and a first bottom header can both be in fluidcommunication with the first hot air circuit, wherein the first topheader can be welded to the first top Y-septum, wherein the first bottomheader can be welded to the first bottom Y-septum; a second top headerand a second bottom header can both be in fluid communication with thesecond hot air circuit, wherein the second top header can be welded tothe first top Y-septum, wherein the second bottom header can be weldedto the first bottom Y-septum; and a third top header and a third bottomheader can both be in fluid communication with the third hot aircircuit, wherein the third top header can be welded to the second topY-septum, wherein the third bottom header can be welded to the secondbottom Y-septum.

An inlet can be fluidly connected to a source of RAM air of theaircraft; and/or an outlet can be fluidly connected to a fan inletdiffuser housing of the ECS.

The first hot air circuit can be configured to direct a first flow ofair, wherein the second hot air circuit can be configured to direct asecond flow of air, wherein the third hot air circuit can be configuredto direct a third flow of air, wherein directions of the first, second,and/or third flows of air can be parallel to a direction of gravity.

A direction of flow of the cold air circuit can be perpendicular todirections of flow of the first, second, and/or third hot air circuits.

A method of transferring thermal energy in an environmental controlsystem includes passing hot air of a first hot air circuit through hotlayers of a first heat exchanger of the environmental control system.Hot air of a second hot air circuit is passed through hot layers of asecond heat exchanger of the environmental control system. Hot air of athird hot air circuit is passed through hot layers of a third heatexchanger of the environmental control system. The first, second, andthird heat exchangers are fluidly connected in series and are brazedtogether to form a single unitized tri-heat exchanger. A cold aircircuit is passed through cold layers of each of the first, second, andthird heat exchangers. A direction of flow of the cold air circuit isperpendicular to directions of flow of the first, second, and third hotair circuits.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingsteps, features, configurations and/or additional components.

Two separate cold air streams can be mixed in an inlet plenum of theenvironmental control system to create a mixed air stream; and/or themixed air stream can be fed into the cold air circuit.

Air from the first heat exchanger can be passed to the third heatexchanger through an external plenum mounted to at least two end wallsof the first, second, and/or third heat exchangers.

The hot air can be passed in a direction that is parallel to gravity.

A heat exchanger assembly for an aircraft includes a bleed air heatexchanger, a fresh air heat exchanger, a chiller heat exchanger, and acold air circuit. The bleed air heat exchanger is in fluid communicationwith a source of bleed air from the aircraft and is configured to directa first flow of air. The fresh air heat exchanger is disposed adjacentto and in fluid communication with the bleed air heat exchanger. Thefresh air heat exchanger is configured to direct a second flow of air.The chiller heat exchanger is disposed adjacent to and in fluidcommunication with the fresh air heat exchanger. The chiller heatexchanger is configured to direct a third flow of air. The bleed air,fresh air, and chiller heat exchangers are brazed together to form asingle unitized tri-heat exchanger. The cold air circuit passes througheach of the bleed air, fresh air, and chiller heat exchangers. Adirection of flow of the cold air circuit is perpendicular to thedirections of the first, second, and third flows of air such that thebleed air, fresh air, and chiller heat exchangers are in cross-flowcommunication with the cold air circuit.

The heat exchanger assembly of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components.

The bleed air, fresh air, and/or chiller heat exchangers can be fluidlyconnected in series.

The directions of flow of the first, second, and third flows of air canbe parallel to a direction of gravity.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A heat exchanger assembly for an aircraft with an environmentalcontrol system, the heat exchanger assembly comprising: a first heatexchanger with a first hot air circuit passing therethrough, wherein thefirst heat exchanger is in fluid communication with a source of bleedair from the aircraft; a second heat exchanger with a second hot aircircuit passing therethrough, wherein the second heat exchanger isdisposed adjacent to and in fluid communication with the first heatexchanger; a third heat exchanger with a third hot air circuit passingtherethrough, wherein the third heat exchanger is disposed adjacent toand in fluid communication with the second heat exchanger, wherein thefirst, second, and third heat exchangers are fluidly connected inseries; and a cold air circuit passing through each of the first,second, and third heat exchangers, wherein the first, second, and thirdheat exchangers are in cross-flow communication with the cold aircircuit.
 2. The heat exchanger assembly of claim 1, wherein the firstheat exchanger comprises a bleed air heat exchanger, wherein the secondheat exchanger comprises a fresh air heat exchanger, and wherein thethird heat exchanger comprises a chiller heat exchanger.
 3. The heatexchanger assembly of claim 1, further comprising: a plurality of hotlayers, wherein each hot layer of the plurality of hot layers comprisesa plurality of hot fins, wherein the first, second, and third hot aircircuits are in fluid communication with the plurality of hot layers;and a plurality of cold layers, wherein each cold layer of the pluralityof cold layers comprises a plurality of cold fins, wherein the cold aircircuit is in fluid communication with the plurality of cold layers. 4.The heat exchanger assembly of claim 1, wherein each cold fin of thepluralities of cold fins is continuous and extends across an entirewidth of the heat exchanger assembly.
 5. The heat exchanger assembly ofclaim 1, wherein the first, second, and third heat exchangers are brazedtogether to form a single unitized tri-heat exchanger.
 6. The heatexchanger assembly of claim 1, further comprising: a first closure bardisposed between the first and second hot air circuits, wherein thefirst closure bar prevents fluid communication across the first closurebar between the first and second hot air circuits; a second closure bardisposed between the second and third hot air circuits, wherein thesecond closure bar prevents fluid communication across the secondclosure bar between the second and third hot air circuits; a first topY-septum welded to a top end of the first closure bar; a second topY-septum welded to a top end of the second closure bar; a first bottomY-septum welded to a bottom end of the first closure bar; and a secondbottom Y-septum welded to a bottom end of the second closure bar.
 7. Theheat exchanger assembly of claim 6, further comprising: a first topheader and a first bottom header both in fluid communication with thefirst hot air circuit, wherein the first top header is welded to thefirst top Y-septum, wherein the first bottom header is welded to thefirst bottom Y-septum; a second top header and a second bottom headerboth in fluid communication with the second hot air circuit, wherein thesecond top header is welded to the first top Y-septum, wherein thesecond bottom header is welded to the first bottom Y-septum; and a thirdtop header and a third bottom header both in fluid communication withthe third hot air circuit, wherein the third top header is welded to thesecond top Y-septum, wherein the third bottom header is welded to thesecond bottom Y-septum.
 8. The heat exchanger assembly of claim 1,wherein the cold air circuit further comprises: an inlet fluidlyconnected to a source of RAM air of the aircraft; and an outlet fluidlyconnected to a fan inlet diffuser housing of the environmental controlsystem of the aircraft.
 9. The heat exchanger assembly of claim 1,wherein the first hot air circuit is configured to direct a first flowof air, wherein the second hot air circuit is configured to direct asecond flow of air, wherein the third hot air circuit is configured todirect a third flow of air, wherein directions of the first, second, andthird flows of air are parallel to a direction of gravity.
 10. The heatexchanger assembly of claim 1, further wherein a direction of flow ofthe cold air circuit is perpendicular to directions of flow of thefirst, second, and third hot air circuits.
 11. A method of transferringthermal energy in an environmental control system, the methodcomprising: passing hot air of a first hot air circuit through hotlayers of a first heat exchanger of the environmental control system;passing hot air of a second hot air circuit through hot layers of asecond heat exchanger of the environmental control system; passing hotair of a third hot air circuit through hot layers of a third heatexchanger of the environmental control system, wherein the first,second, and third heat exchangers are fluidly connected in series, andwherein the first, second, and third heat exchangers are brazed togetherto form a single unitized tri-heat exchanger; and passing cold air of acold air circuit through cold layers of each of the first, second, andthird heat exchangers, wherein a direction of flow of the cold aircircuit is perpendicular to directions of flow of the first, second, andthird hot air circuits.
 12. The method of claim 11, further comprising:mixing two separate cold air streams in an inlet plenum of theenvironmental control system to create a mixed air stream; and feedingthe mixed air stream into the cold air circuit.
 13. The method of claim11, further comprising: passing air from the first heat exchanger to thethird heat exchanger through an external plenum mounted to at least twoend walls of the first, second, and third heat exchangers.
 14. Themethod of claim 11, wherein passing the hot air through the hot layersof the first, second, and third heat exchangers comprises passing thehot air in a direction that is parallel to gravity.
 15. A heat exchangerassembly for an aircraft, the heat exchanger assembly comprising: ableed air heat exchanger in fluid communication with a source of bleedair from the aircraft; a fresh air heat exchanger disposed adjacent toand in fluid communication with the bleed air heat exchanger; a chillerheat exchanger disposed adjacent to and in fluid communication with thefresh air heat exchanger, wherein the bleed air, fresh air, and chillerheat exchangers are brazed together to form a single unitized tri-heatexchanger; and a cold air circuit passing through each of the bleed air,fresh air, and chiller heat exchangers, wherein: the bleed air heatexchanger is configured to direct a first flow of air; the fresh airheat exchanger is configured to direct a second flow of air; the chillerheat exchanger is configured to direct a third flow of air, wherein adirection of flow of the cold air circuit is perpendicular to thedirections of the first, second, and third flows of air such that thebleed air, fresh air, and chiller heat exchangers are in cross-flowcommunication with the cold air circuit.
 16. The heat exchanger assemblyof claim 15, wherein the bleed air, fresh air, and chiller heatexchangers are fluidly connected in series.
 17. The heat exchangerassembly of claim 15, wherein the directions of flow of the first,second, and third flows of air are parallel to a direction of gravity.